US7242351B2 - Real-time emitter locating system and method - Google Patents
Real-time emitter locating system and method Download PDFInfo
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- US7242351B2 US7242351B2 US10/785,353 US78535304A US7242351B2 US 7242351 B2 US7242351 B2 US 7242351B2 US 78535304 A US78535304 A US 78535304A US 7242351 B2 US7242351 B2 US 7242351B2
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- transmitter
- real
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- bearing
- determining
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S5/00—Position-fixing by co-ordinating two or more direction or position line determinations; Position-fixing by co-ordinating two or more distance determinations
- G01S5/02—Position-fixing by co-ordinating two or more direction or position line determinations; Position-fixing by co-ordinating two or more distance determinations using radio waves
- G01S5/04—Position of source determined by a plurality of spaced direction-finders
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S5/00—Position-fixing by co-ordinating two or more direction or position line determinations; Position-fixing by co-ordinating two or more distance determinations
- G01S5/02—Position-fixing by co-ordinating two or more direction or position line determinations; Position-fixing by co-ordinating two or more distance determinations using radio waves
- G01S5/0205—Details
- G01S5/021—Calibration, monitoring or correction
Definitions
- This invention relates generally to Emitter Locating Systems and, more specifically, to a Real-time Emitter Locating System and Method
- Emitter Location (EL) Systems are used to locate the position of emitting radio transmitters.
- finding the location of a radio transmitter involves triangulation methods using at least three radio Direction Finding (DF) “Sets”.
- DF radio Direction Finding
- the DF Sets that comprise EL Systems produce uncertainties in their measurements due to several factors which will be described later.
- the invention of this disclosure provides a far more accurate method of operating EL Systems than is presently done today.
- present day EL Systems are comprised of multiple radio Direction Finding (DF) Sets which can either be fixed in location, or mobile on a vehicle, ship, aircraft, etc.
- DF radio Direction Finding
- the invention of this disclosure especially relates to EL Systems employing at least one mobile DF Set.
- only a single mobile DF Set is required in an EL System.
- the background of direction finding operations needs to covered.
- the basic components of a DF Set are: (1) a DF antenna array; and (2) a DF receiver/processor (hereafter referred to simply as “DF receiver”).
- the basic components of an EL System are: (1) at least one DF Set; (2) some device to interpret the streaming Line-Of-Bearing (LOB) data sets from the DF Set; (3) some sensor device to determine the DF Set's location; and (4) some sensor device to output the DF Set's orientation relative to true North.
- LOB Line-Of-Bearing
- the major sources of measurement errors in real-world DF Sets are: (1) uncertainties from the DF antenna array due to frequency dependent variations; and (2) received signal reflections (also known as multi-path).
- a device is attached to the output that collects, interprets, and plots the line-of-bearing (LOB) data.
- This device is typically a computer which then displays the LOB's on some sort of map display.
- the LOBs that are displayed will vary from measurement to measurement depending on the aforementioned uncertainties.
- the DF Sets simply take the collected LOB data sets and average them to produce a best guess as to the true LOB to the transmitter. But as mentioned, the resulting LOB invariably has some level of error, which translates to errors in overall determination of the transmitter's location.
- the invention described in this disclosure uses an improved method and technique to collect data from one or multiple DF Sets, and then to intelligently process that data in real time so that overall measurement uncertainties are reduced.
- the transmitter's position plotted on a map will be more accurate. It should be reiterated that with the method and technique of this invention, it is possible to determine, and continuously plot on a map, the location of a transmitter by using only a single DF Set. This fact makes this invention further unique.
- the preferred system should provide a technique for taking in data sets (lines of bearing) from DF receivers and characterizing those signals with their respective probabilities of error. Then using a unique method, the preferred system can apply a recursive processing technique to this continuous stream of data, displaying transmitter positions with significantly less uncertainty. Furthermore, the preferred system must be able to perform these functions in real-time. It is a further object that this system is capable of being fully automated which would reduce the processing time and reduce the necessity of human intervention.
- an alternative embodiment of the present invention is to feasibly remote control the system over a network and collect and combine the same information from several DF Sets.
- a far more efficient EL System can be achieved in which the emitter's position can be determined more quickly from a centralized command facility.
- This combination of data filtering and data collection techniques significantly reduces measurement uncertainties and enhances the accuracy of EL systems.
- FIG. 1 is a drawing of a typical DF Set
- FIG. 2 is a drawing of the configuration of an EL System when employing the method of this invention
- FIG. 3 is a drawing of how emitter locating is presently done today with three or more DF Sets
- FIG. 4 is a drawing of the technique of this invention for collecting data
- FIG. 5 is a flow chart depicting the prior art DF method for locating a transmitter
- FIGS. 6A and 6B depicts the graphical approach employed by the present invention to determine a transmitter's position point
- FIG. 7 is a flow chart depicting the real-time DF method for locating a transmitter of the present invention.
- FIG. 1 is a drawing of a typical DF Set 10 .
- a DF Set 10 is comprised of a DF antenna 16 which is connected to a DF receiver 18 .
- the DF receiver then outputs LOB data 20 .
- the output LOB measurements are either raw data, or averaged data.
- FIG. 2 is a drawing of the configuration of an EL System when employing the method of this invention.
- a single DF Set has its output LOB's and quality number data sent to a computer which runs the method of this invention. Other data from a GPS sensor and a Compass are also used.
- An EL System is comprised of a DF Set which outputs its LOB data to a computer device 26 .
- the computer also gets DF Set position data 24 from a positioning device 22 (which is often a GPS sensor), as well as DF Set orientation data 25 from a compass device 23 .
- the computer 26 provides the following functions for the EL System: (1) Algorithms on the LOB data sets to reduce measurement uncertainties; (2) DF receiver control; (3) Mapping and LOB histogram displays; (4) Antenna calibration tables; (5) Networking capabilities; and (6) Integrated triangulation functions with other mobile/fixed DF Sets.
- FIG. 3 is a drawing of how emitter locating is presently done today with three or more DF Sets.
- the DF Sets are connected through a communications link so the LOB data from each DF Set is used to triangulate the position of the transmitter.
- the result is a transmitter's location that sometimes contains large uncertainties.
- FIG. 4 is a drawing of the technique of this invention for collecting data.
- at least one of the DF Sets is mobile. Only one is shown in FIG. 4 , the mobile unit can be a part of a larger network of more DF Sets though.
- the transmitter's position is calculated much more accurately and in real-time with a combination of data-taking technique and the specialized method to handle the data streams. The result is a transmitter's location that contains reduced uncertainties and errors and is more accurate.
- the technique of this invention involves the use of a mobile DF Set in a EL System. There may be one or multiple DF Sets used.
- the first step is for the mobile DF Set to take an LOB measurement of transmitter 12 .
- This process involves taking the LOB data and the so-called “quality number” reading from the DF receiver.
- Modem DF receivers now produce a quality number with every LOB output. This quality number value is a metric by which the DF receiver manufacturer estimates the probability that a measurement is accurate.
- the computer 26 then takes this quality number along with the actual LOB measurement and stores them in memory for future processing.
- the next step is for the mobile DF Set to move its physical position with respect to the transmitter's position. While moving, the DF Set is constantly taking in more LOB data and associated quality numbers. This process goes on for as long as required to find the transmitter. The more data that is collected, the higher will be the probability that the triangulated position of the transmitter is where it is expected to be.
- This invention employs a specialized recursive method in the computer to process the LOB data that is continually being stored. The whole process begins after a “cross-over” point is first found.
- a cross-over point is the intersection between the last best LOB data entry, and the newly arrived LOB; typically a point where two LOB's cross (a position having a fairly high confidence level).
- This cross-over point when fixed on a map, is the original triangulated position (hereafter referred to as the “position point”) of the transmitter.
- a new LOB is measured and taken into account.
- the method calculates the shortest distance between the last best position point, and the newly arrived LOB. This will be a perpendicular vector from the point to the line-of-bearing.
- the method then calculates a new best guess position point along this vector, taking into account the new LOB's associated quality number as a weighting. Again, this calculation can be done in real time since the method is recursive, and therefore does not require the recomputing of every single LOB data entry taken up to that point.
- the method uses a form of feedback control with an expected outcome.
- This recursive process is the basis of the method's uniqueness when applied to reducing measurement uncertainties in EL Systems.
- the measurement update steps of the method are responsible for incorporating every new measurement into the a priori estimate to obtain an improved a posteriori estimate.
- the method then outputs the “adjusted” output accordingly given the continuous stream of data points. This process will in effect prioritize the higher probability measurements designated by the quality number.
- the computer displays to the EL operator a much more accurate fix to the transmitter than can be achieved by simple averaging means of the entire data sets.
- the method of this invention is a form of statistical filtering.
- This method has the ability to do real-time processing. Simple averaging of values requires more multiplications, thus the old method of averaging is slower and not able to be used in real-time if a large amount of data is used.
- the newer method of this provisional patent application uses fewer multiplications and thus can be performed by any standard processor and computer. To reiterate, the method's recursive nature thus makes practical implementations much more feasible than simple averaging, which is designed to operate on all of the data directly for each estimate. This is a unique and distinguishing advantage of the invention when used in EL Systems.
- FIG. 5 is a flow chart depicting the prior art DF method for locating a transmitter.
- the EL system receives a stream of Line of Bearing and Quality information from at least three DF sets 42 A, 42 B and 42 C; three DF sets is generally the minimum necessary in order to achieve triangulation.
- the EL system calculates the average Line of Bearing from a particular segment of each DF set 44 A, 44 B and 44 C. These averaged Lines of Bearing from each DF set to the transmitter are then plotted 46 to result in a conclusion by the EL system as to the transmitter's location 48 .
- the target problems to be resolved by the present invention is the delay in arriving at the average Line of Bearing for each DF set, the lack of control and understanding of the inherent error in each of the LOB averages, and also the need for three or more active and high-quality DF set LOB signals in order to arrive at any sort of reliable transmitter position.
- FIG. 6A shows the fundamentals of how the present approach operates.
- FIG. 6A depicts the DF set at two subsequent locations.
- the DF set is shown as stationary (relative to the transmitter location graphical solution).
- FIG. 6A can be considered to be a DF Set-centric view, wherein the DF set appears to be stationary and any lines of bearing or transmitter locations are in relation (or relative to) the moving DF set.
- the transmitter might actually be stationary in the depicted FIG. 6 , with all relative movement being provided by the transmitter.
- PP( 0 ) (the cross-over point) is determined as discussed in the Specification previously.
- the line of bearing to the cross-over point will continue to “point” towards PP( 0 ).
- a new DF Set location is reached and a new line of bearing is “drawn” to the newly-detected transmission.
- the connecting vector in this example, is then drawn perpendicular to the latest line of bearing, through the last line of bearing or estimate position (in this case it is PP( 0 )).
- FIG. 6B graphically depicts the method of the present invention (as specifically described below in connection with the description associated with FIG. 7 ), from an “Earth-centric” or reference frame fixed in relation to the earth.
- the EL system obtains another Line of Bearing (LOB( 1 )) to the transmitter (PP( 1 )), and constructs a connecting vector 52 that is perpendicular to the current line of bearing (LOB( 1 )), and ends at the last line of bearing (in this case, PP( 0 ), the cross-over point).
- This method assumes that the higher the quality number associated with LOB( 1 ), the higher the probability that PP( 1 ) actually lies on the connecting vector 52 . This process is repeated, and more LOB's are obtained, until such time as the EL system determines a high probability of the location of the transmitter.
- FIG 6 depicts the DF set at two subsequent locations.
- the DF set is shown as stationary (relative to the transmitter location graphical solution).
- FIG. 6 can be considered to be a DE Set-centric view, wherein the DF set appears to be stationary and any lines of bearing or transmitter locations are in relation (or relative to) the moving DF set.
- the transmitter might actually be stationary in the depicted FIG. 6 , with all relative movement being provided by the transmitter.
- PP( 0 ) (the cross-over point) is determined as discussed in the Specification previously. As the DF Set is then moved, the line of bearing to the cross-over point will continue to “point” towards PP( 0 ).
- the connecting vector in this example, is then drawn perpendicular to the latest line of bearing, through the last line of bearing or estimate position (in this case it is PP( 0 )).
- the DF set 10 must be exhibit motion relative to the transmitter, so that the LOB's will change somewhat as more and more readings are taken; (2) there is no need for three or even two DF sets in order to determine a “fix” or actual position for the transmitter with this method; and (3) all position determinations are made “on the fly,” in real-time.
- FIG. 7 we can see how the entire method of the present invention executes.
- FIG. 7 is a flow chart depicting the real-time DF method 54 for locating a transmitter of the present invention.
- DF set( 1 ) is relocated again 60 B, and another transmission is received and LOB generated, until such time as when two sequential LOB's do cross one another.
- DF set( 1 ) is relocated again 60 C, and another transmission is received from transmitter( 1 ) 56 C.
- Another LOB is generated 58 C representing the direction to transmitter( 1 ) from DF set( 1 ).
- a “connecting vector” (see FIG. 6 ) is generated from the last “Best Guess” location to the latest LOB 66 .
- a “New Best Guess” location is generated along the connecting vector, with its proximity to the last best guess being determined by the quality number of the latest transmission (and LOB), weighed against the weight of the last best guess (which is a factor of sample size and quality of the data that led to the last best guess's location).
- the New Best Guess location will be identified for the user as transmitter( 1 )'s location 70 , updated in real-time (unlike the prior systems).
- the system 54 then continues to relocate the DF set 60 D and receive transmissions in order to continue to determine the location of transmitter( 1 ).
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US10/785,353 US7242351B2 (en) | 2003-02-24 | 2004-02-24 | Real-time emitter locating system and method |
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US10/785,353 US7242351B2 (en) | 2003-02-24 | 2004-02-24 | Real-time emitter locating system and method |
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Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20060036563A1 (en) * | 2004-08-12 | 2006-02-16 | Yuh-Cherng Wu | Knowledge network generation |
WO2014195164A3 (en) * | 2013-06-04 | 2015-09-24 | Pps Gmbh | Localization system for monitoring objects in real-time |
Families Citing this family (9)
Publication number | Priority date | Publication date | Assignee | Title |
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DE602004012620T2 (en) * | 2004-05-28 | 2009-04-23 | Telefonaktiebolaget Lm Ericsson (Publ) | DIGITALISIERERANORDNUNG |
US7565156B2 (en) | 2004-08-11 | 2009-07-21 | Agilent Technologies, Inc. | Method and technique for the processing and display of wideband geolocation determination data |
US7724680B2 (en) * | 2004-08-11 | 2010-05-25 | Agilent Technologies, Inc. | Method and technique for the processing and intelligent display of wideband direction-finding data |
DE102008016137A1 (en) * | 2007-11-19 | 2009-05-20 | Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V. | Device for locating objects or persons, in particular for an avalanche spill search and method for locating |
FR2926143B1 (en) * | 2008-01-07 | 2013-12-13 | Nexter Systems | METHOD OF SLEEPING AND DETECTING TARGETS, PARTICULARLY MOBILE, FOR A PLATFORM AND DEVICE IMPLEMENTING SAID METHOD |
US20130053056A1 (en) * | 2011-08-29 | 2013-02-28 | Qualcomm Incorporated | Facilitating mobile device positioning |
US10620296B1 (en) * | 2017-01-03 | 2020-04-14 | Toyon Research Corporation | System for positioning, navigation, and time (PNT) |
JP2018179919A (en) * | 2017-04-20 | 2018-11-15 | ラピスセミコンダクタ株式会社 | Position estimation method, position estimation device, and position estimation system |
US11899122B2 (en) * | 2020-12-10 | 2024-02-13 | Assured Information Security, Inc. | Geolocating emitters |
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US5343212A (en) * | 1992-12-11 | 1994-08-30 | Litton Industries, Inc. | (AOA/LBI) emitter ranging method and apparatus |
US6249252B1 (en) * | 1996-09-09 | 2001-06-19 | Tracbeam Llc | Wireless location using multiple location estimators |
US20040029558A1 (en) * | 2002-08-06 | 2004-02-12 | Hang Liu | Method and system for determining a location of a wireless transmitting device and guiding the search for the same |
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- 2004-02-24 US US10/785,353 patent/US7242351B2/en not_active Expired - Fee Related
Patent Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5343212A (en) * | 1992-12-11 | 1994-08-30 | Litton Industries, Inc. | (AOA/LBI) emitter ranging method and apparatus |
US6249252B1 (en) * | 1996-09-09 | 2001-06-19 | Tracbeam Llc | Wireless location using multiple location estimators |
US20040029558A1 (en) * | 2002-08-06 | 2004-02-12 | Hang Liu | Method and system for determining a location of a wireless transmitting device and guiding the search for the same |
Cited By (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20060036563A1 (en) * | 2004-08-12 | 2006-02-16 | Yuh-Cherng Wu | Knowledge network generation |
US7310625B2 (en) * | 2004-08-12 | 2007-12-18 | Sap Aktiengesellschaft | Knowledge network generation |
WO2014195164A3 (en) * | 2013-06-04 | 2015-09-24 | Pps Gmbh | Localization system for monitoring objects in real-time |
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US20040164901A1 (en) | 2004-08-26 |
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